public static void TestIsAndAs()
{
SerializableObject sobj = new Umbrella();
//...
//sr.SerializeToFile(...);
//sr.Price = 200;
ChangeObject(ref sobj);
// Using "is".
if (sobj is Umbrella)
{
Umbrella um = (Umbrella)sobj;
um.Price = 200;
um.Ean = "123468904";
um.Type = "automatic";
}
// Using "is".
if (sobj is StockItem)
{
StockItem si = (StockItem)sobj;
si.Price = 200;
// Uncommenting this line causes a compile-time error.
// A StockItem might be an umbrella, but it may also be an anorak, a pencil, whatever we sell on our e-shop.
//si.Type = "automatic";
}
// Using "as".
Anorak anorak = sobj as Anorak;
if (anorak != null)
{
Console.WriteLine(anorak.Size);
}
// Using "as".
// This compiles fine because SerializableObject and UserPreferences have a relationship "ancestor-descendant".
UserPreferences preferences = sobj as UserPreferences;
if (preferences != null)
{
preferences.Theme = Theme.Orange;
}
// Using "as".
// This compiles fine because SerializableObject and StockItem have a relationship "ancestor-descendant".
StockItem item = sobj as StockItem;
if (item != null)
{
// The following lines do NOT compile because StockItem and UserPreferences do NOT have a relationship "ancestor-descendant".
// The two types lie in different branches of the object hierarchy.
//UserPreferences up = item as UserPreferences;
//up.IsConfirmDelete = false;
}
}
private static void ChangeObject(ref SerializableObject obj)
{
obj = new Anorak();
}